1. Technical Field
This disclosure relates to printing systems and processes, and more particularly to methods and systems for variable data imaging.
2. Description of the Related Art
Many current plate-based printing systems such as offset, screen, and flexographic presses can benefit from a way to introduce variable data without having to invest in new capital equipment, by finding a clean way of utilizing existing offset, screen, or flexographic printing infrastructure and marking materials to form variable data images. Today hybrid printing approaches involve continuous ink jet (CIJ) or drop on demand (DOD) inkjet matched with traditional inline flexographic, screen, or offset printing units. Hybrid systems make sense as an investment when most variable data information is a subset of a large static image. Thus, for bar coding, addressing, some personalization, security codes, or some short run print design alterations, such hybrid approaches make sense.
Unfortunately, most hybrid systems on the market today suffer from the issue that it is very challenging to use process colors to color match a spot color that is usually printed by flexo, screen, or offset processes using a static, plate-based approach. This is because the process colors are usually of a fundamentally different chemistry. Also, achieving repeatable matching of a spot color with four color processes is very difficult to control without extensive trial and error, which results in numerous wasted substrates. Furthermore, it is also impossible to match the exact gloss of inkjet inks with the screen, flexo, or litho inks used to form a static background image because the pile height and the extent of bleed into the substrate (bleed-through) are different for different ink chemistries.
For example, CIJ and DOD are usually water-based inks, which can have bleed-through issues due to the low viscosity of the ink. Water-based inks also do not perform well on metallic or plastic substrates. In addition, for packaging and textile applications, no one has been able to formulate ink-jettable materials which are a brilliant titanium white or a shiny metallic with luster that match those in the flexographic and screen-printing processes.
Ultra-Violet (UV) inkjet machines have less of a bleed through issue but often have color gamut and color matching issues due to the amount of photoinitiators or acrylate based monomers which must be loaded into the ink as well as carrier fluids necessary to lower the viscosity of the ink so that it can be jetted. For example, pigment loading is usually far less for inkjettable inks. It is interesting that very high resolution has been achieved with inkjet technologies and it is not a primary technical barrier that limits the penetration of UV inkjet technologies into the packaging market. Instead, the far greater technical barrier is one of spot color matching for satisfying branding requirements. Some hybrid solutions are relying on a 6 or 8 variable data CIJ color process in order to approximate imprinted color matching with a background image printed with only a single spot color flexographic ink run, wherein the flexographic ink has a much lower print cost. It is this spot color requirement that is limiting full market penetration of hybrid solutions into some flexographic applications such as flexible/film product substrates or corrugated.
One example of the need to print variable data with spot colors includes business card applications where an exact match of the company logo color is important for branding purposes. Thus, most business cards print jobs are ordered in large queued up batches at a commercial printer in order to minimize the number of plates needed for offset printing. Digital techniques allow ordering on demand but can not often provide good enough color matching to be acceptable for company logos. This is especially true when metallic colors are used.
Another example is in the area of high-scale boutique rebranding where a low end product is sold at a substantial markup by repackaging it in a highly attractive label. The products are then resold at a high end boutique store or for special upscale events such as weddings or conferences. The ability to introduce variable data with metallic luster inks for special events would be a tremendous added advantage over other hybrid systems.
The T-shirt screen printing market is another good example where variable data printing of an individual name in a spot color matching the spot color of a company logo is ideal but not economically realizable with current digital printing technologies. Example embodiments of the invention address these and other disadvantages of the related art.